1. Field of the Invention
The invention relates to a unitary solar collector module comprising a rigid frame and glass collector tubes supported thereby.
2. Description of the Prior Art
Tubular glass collectors for radiant solar energy are becoming increasingly popular as an alternative to flat plate solar collectors. Glass collector tubes such as those employed in the OWENS-ILLINOIS, INC. "Sunpak" system comprise three coaxial glass tubes are disclosed in U.S. Pat. Nos. 4,033,327 and 4,043,318 to Pei and U.S. Pat. No. 4,262,658 to Frissora. The annulus between the inner two tubes contains the heat transfer fluid. The intermediate tube of the three is exposed to solar radiation, and is coated with a solar selective energy absorbing coating. Impinging solar radiation is converted on this surface to thermal energy for heating the fluid inside the intermediate tube. The innermost tube provides for fluid flow into or out of the collector tube. The annulus between the outer and the intermediate tubes is evacuated to prevent convection losses.
A system utilizing such tubes in series includes a manifold directing fluid flow successively from the outlet of one collector tube to the inlet of an adjacent collector tube. See, for example, the aforementioned Pei U.S. Pat. No. 4,033,327. A parallel flow arrangement of collector tubes is shown in the Frissora U.S. Pat. No. 4,262,658. The seals between the openings of the collector tubes and the manifold conduits are maintained by gaskets within the manifold. To prevent leakage in any such systems, a precise alignment of the collector tubes and the manifold is necessary. Heretofore, when installing a glass tube solar collector system on a roof, for example, the manifold has been installed, then the collector tubes were individually mounted and aligned during the installation of the separate frame elements supporting the tubes. In such an installation process, considerable on site skilled work is required.
A modular frame is obviously desirable to facilitate the installation of such a system of glass solar collector tubes. The frame must be lightweight for ease of installation and economy, yet sufficiently rigid to protect the glass collector tubes from excess bending or compressive forces due to mishandling of the frame, such as lifting by a corner, and to maintain the alignment of the tubes and manifold and the integrity of the seals. Furthermore, it is desirable that the frame be attached to an associated roof or other structure at as few points as possible, consistent with a completely secure attachment.
The aforesaid U.S. Pat. No. 4,262,658 to Frissora discloses the use of tension rods between tube support members at either ends of the collector tubes in a conventional installation, but does not disclose a reinforced modular frame.